do we have a way of making a data class that utilize `Either` for the validation and has a sensible ...

# arrow

[Rohde Fischer]

do we have a way of making a data class that utilize Either for the validation and has a sensible copy without one having to do too many manual overrides. I.e., one could do for construction:

data class Foo private constructor(val x: Int) {
    companion object {
        fun create(x: Int): Either<Error, Foo> { /* domain logic for new foo */ }
    }
}

or its sibling with operator fun invoke

but what about copy? That will still expose my private and unsafe constructor. I could of course do the validation in an init as well and "bite the bullet" having an exception throwing copy 😕 but I'd much rather have a copy using the create function or invoke

[Youssef Shoaib [MOD]]

Newest Kotlin update has @ConsistentCopyVisibility or something like that. That'll at least hide the default copy, then you can define your own. Also, I'd suggest having your methods taking a Raise receiver instead for convenience

[Rohde Fischer]

hmm, at least better 🙂

where can I read about Raise receivers?

[Youssef Shoaib [MOD]]

https://arrow-kt.io/learn/typed-errors/from-either-to-raise/

[Rohde Fischer]

thanks

[Riccardo Cardin]

https://blog.rockthejvm.com/functional-error-handling-in-kotlin-part-3/

[Rohde Fischer]

@Riccardo Cardin thanks to you too 🙂